简单的分页查询

步骤一：引入依赖

在项目的构建文件（例如Maven的pom.xml）中添加MyBatis-Plus的依赖：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.buba</groupId>
    <artifactId>mybatisplus-maven</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <artifactId>spring-boot-starter-parent</artifactId>
        <groupId>org.springframework.boot</groupId>
        <version>2.7.6</version>
    </parent>

    <properties>
        <maven.compiler.source>11</maven.compiler.source>
        <maven.compiler.target>11</maven.compiler.target>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>8.0.23</version>
        </dependency>
        <dependency>
            <groupId>com.baomidou</groupId>
            <artifactId>mybatis-plus-boot-starter</artifactId>
            <version>3.4.3</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
    </dependencies>

</project>

步骤二：配置类

package com.buba.config;


import com.baomidou.mybatisplus.annotation.DbType;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.extension.plugins.MybatisPlusInterceptor;
import com.baomidou.mybatisplus.extension.plugins.inner.PaginationInnerInterceptor;
import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
@ConditionalOnClass({MybatisPlusInterceptor.class, BaseMapper.class})
public class MybatisConfig {

    @Bean
    @ConditionalOnMissingBean
    public MybatisPlusInterceptor mybatisPlusInterceptor() {
        MybatisPlusInterceptor interceptor = new MybatisPlusInterceptor();
        PaginationInnerInterceptor paginationInnerInterceptor = new PaginationInnerInterceptor(DbType.MYSQL);
        // 设置最大限制为200
        paginationInnerInterceptor.setMaxLimit(200L);
        // 添加分页插件到拦截器链中
        interceptor.addInnerInterceptor(paginationInnerInterceptor);
        return interceptor;
    }
}

步骤三：yml文件

server:
  port: 8992
spring:
  datasource:
    driver-class-name: com.mysql.cj.jdbc.Driver
    url: jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&serverTimezone=Asia/Shanghai
    username: root
    password: 123456

步骤四：实体类

创建对应数据库表的实体类，并使用MyBatis-Plus的注解进行配置。例如，使用@TableName注解指定表名，使用@TableId注解指定主键。

package com.buba.damain.po;

import com.baomidou.mybatisplus.annotation.TableName;
import com.baomidou.mybatisplus.annotation.IdType;
import com.baomidou.mybatisplus.annotation.TableId;
import java.io.Serializable;
import lombok.Data;
import lombok.EqualsAndHashCode;
import lombok.experimental.Accessors;

/**
 * <p>
 * 
 * </p>
 *
 * @author bilal
 * @since 2023-08-29
 */
@Data
@EqualsAndHashCode(callSuper = false)
@Accessors(chain = true)
@TableName("student")
public class Student implements Serializable {

    private static final long serialVersionUID = 1L;

    @TableId(value = "id", type = IdType.AUTO)
    private Integer id;

    private String name;

    private Integer age;

    private Integer classId;

    private Integer score;
    
}

表结构：

CREATE TABLE `student`  (
  `id` int NOT NULL AUTO_INCREMENT,
  `name` varchar(50) CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci NOT NULL,
  `age` int NOT NULL,
  `class_id` int NULL DEFAULT NULL,
  `score` int NULL DEFAULT NULL,
  PRIMARY KEY (`id`) USING BTREE,
  INDEX `class_id`(`class_id` ASC) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 10 CHARACTER SET = utf8mb4 COLLATE = utf8mb4_0900_ai_ci ROW_FORMAT = Dynamic;

步骤五：Mapper接口

创建继承自MyBatis-Plus的BaseMapper接口的自定义Mapper接口。该接口无需编写任何方法，MyBatis-Plus会根据实体类的注解自动生成基本的增删改查方法。

package com.buba.mapper;

import com.buba.damain.po.Student;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;

/**
 * <p>
 *  Mapper 接口
 * </p>
 *
 * @author bilal
 * @since 2023-08-29
 */
public interface StudentMapper extends BaseMapper<Student> {

}

步骤六：service层

package com.buba.service;

import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.buba.damain.po.Student;
import com.baomidou.mybatisplus.extension.service.IService;

public interface IStudentService extends IService<Student> {

    Page<Student> queryStudent(Integer pageNo, Integer pageSize);

}

步骤七：分页查询

package com.buba.service.impl;


import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.buba.damain.po.Student;
import com.buba.mapper.StudentMapper;
import com.buba.service.IStudentService;
import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import org.springframework.stereotype.Service;

@Service
public class StudentServiceImpl extends ServiceImpl<StudentMapper, Student> implements IStudentService {

    @Override
    public Page<Student> queryStudent(Integer pageNo, Integer pageSize) {
        Page<Student> page = new Page<>(pageNo, pageSize);
        return lambdaQuery()
                .gt(Student::getScore,60)
                .page(page);
    }
}

步骤八：前端控制器

package com.buba.controller;

import com.baomidou.mybatisplus.extension.plugins.pagination.Page;
import com.buba.damain.po.Student;
import com.buba.service.IStudentService;
import lombok.RequiredArgsConstructor;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/student")
@RequiredArgsConstructor
public class StudentController {
    private final IStudentService studentService;
    
    @GetMapping("/page")
    public Page<Student> queryStudent(@RequestParam(value = "pageNo", defaultValue = "1") Integer pageNo,
                                       @RequestParam(value = "pageSize", defaultValue = "5") Integer pageSize) {
        return studentService.queryStudent(pageNo, pageSize);
    }
}

步骤九：启动类

package com.buba;

import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
@MapperScan("com.buba.mapper")
public class MybatisApplication {
    public static void main(String[] args) {
        SpringApplication.run(MybatisApplication.class,args);
    }
}